Fluorine-containing (meth)acrylic esters such as CH2═CHCO2CH2CH2—Rf or CH2═C(CH3) CO2CH2CH2—Rf have been used in a large amount as a raw material monomer of a water and oil repellent for fibers. In recent years, however, use of the monomers having a perfluoroalkyl group (Rf) of 8 or more carbon atoms have become difficult because such monomers have high bioaccumulation potential. In order to avoid this problem, use of fluorine-containing (meth)acrylic esters having a perfluoroalkyl group of 6 or less carbon atoms have been recommended. As one example, a fluorine-containing block copolymer using a fluorine-containing (meth)acrylic ester having a perfluoroalkyl group of 6 or less carbon atoms has been reported (Patent documents 1 to 5).
However, the fluorine-containing block copolymers produced by the use of, as a raw material, a fluorine-containing (meth)acrylic ester having a perfluoroalkyl group of 6 or less carbon atoms did not exhibit satisfactory water and oil repellency in some cases.
On the other hand, with regard to block polymer production technology, precise control of molecular weight, molecular end, molecular weight distribution and molecular chain molecular arrangement has become possible with the progress of living radical polymerization technology. Particularly, controlled living radical polymerizations, such as reversible addition fragmentation chain transfer polymerization (RAFT polymerization), atom transfer radical polymerization (ATRP) or nitroxide-mediated radical polymerization (NMP), have a merit of no need for low-temperature polymerization or strict purification of monomers in anionic polymerization or the like, and a merit of a wide application range of monomers. Moreover, there is an advantage that the polymerization can be readily carried out under usual radical polymerization conditions (industrial versatility), and it has become possible to readily prepare block copolymers having various structures and functions (Non-patent Documents 1 to 3).
Among them, the Non-patent Document 1 describes that various studies of RAFT polymerization, including examination of reaction mechanism, examination of reactivity due to substituents, etc., have been made. The Non-patent Document 2 describes that various studies have also been made for ATRP. The Non-patent Document 3 describes an attempt to control polymerization of a variety of vinyl-based monomers by means of nitroxide-mediated living free radical polymerization.